1. Field of the Invention
The present invention relates to a housing structure of a distributor for an internal combustion engine including an ignition coil.
2. Description of the Related Art
FIG. 1 shows a longitudinal section of a distributor for an internal combustion engine which includes an ignition coil for generating high voltage supplied to the spark plugs of the engine.
The distributor may be divided into rotating and stationary portions. The rotating portion of the distributor comprises: a shaft 1 rotating in synchronism with the crankshaft of an internal combustion engine; a spark advancing sleeve 2 rotatably mounted on the shaft 1; a centrifugally-operated spark advancing mechanism 3 operatively coupling the spark advancing sleeve 2 to the shaft 1; a distributor rotor 4 fixed to the spark advancing sleeve 2 and including a brush 4a and a rotor electrode 4b; and a reluctor 5 in the form of a reluctance varying rotor formed of a magnetic material, the reluctor 5 having a plurality of projections extending radially outwardly from the outer circumferential surface thereof so that the reluctance therethrough is varied in synchronism with the rotation thereof.
The stationary portion of the distributor comprises: a cup-shaped housing base 6; an ignition coil 7 having a high-voltage tower 8 for outputting the high voltage from the secondary winding of the ignition coil 7; a housing cap 9 having an insertion electrode 9a fitted into a bore which is formed in the high-voltage tower 8, a central electrode 9b for supplying high voltage to the brush 4a of the distributor rotor 4, and a plurality of circumferentially spaced fixed electrodes 9c to which high voltage is supplied from the rotor electrode 4b; a vacuum-operated spark advancing mechanism 13 having a spark advancing annular plate 14 rotatably supported by the housing base 6; an ignition timing sensor 15 fixedly mounted on the spark advancing plate 14 in a spaced opposed relation with the reluctance varying rotor 5; and a waterproofing and leakage preventing cover 10 separating the high voltage distributing portion from the spark advancing mechanisms, etc., the cover 10 being held between the housing base 6 and the cap 9 through the intermediary of an annular sealing members 11 and 12.
In operation, the angle advancing sleeve 2, which carries the reluctance varying rotor 5 and the distributor rotor 4, is driven by the shaft 1 through the intermediary of the centrifugally-operated spark advancing mechanism 3 so that the rotational angle of the sleeve 2 is advanced in proportion to the rotational speed of the shaft 1 through the intermediary of the centrifugally-operated spark advancing mechanism 3. On the other hand, the relative rotational position of the sensor 15 with respect to the housing is advanced by the vacuum-operated spark advancing mechanism 13, which adjusts the rotational position of the annular plate 14. Thus, the sensor 15, which detects the variation of the magnetic flux caused by the variation of the reluctance through the rotating rotor 5, generates an ignition timing signal at the optimum rotational position of the crankshaft of the internal combustion engine. The breaking and making of the current through the primary winding of the ignition coil is controlled by the ignition timing signal outputted from the sensor 15. The high voltage developed in the secondary winding of the ignition coil 7 is taken out from the high voltage tower 8 and supplied therefrom to the distributor rotor 4 through the insertion terminal 9a, the central electrode 9b, and the brush 4a.
In the housing structure shown in FIG. 1, the cover 10 is interposed between the housing base 6 and the housing cap 9 for two purposes; first, for preventing the high voltage applied to the rotor electrode 4b and the fixed electrodes 9c from leaking into the space thereunder accommodating the spark advancing mechanisms, etc.; second for preventing water from reaching the high-voltage distributing portion thereabove, when water enters from ventilating holes (not shown) formed around the spark advancing mechanisms, etc. Further, the high-voltage tower 8 comprises a deep recess into which the insertion electrode 9a is fitted, so that the high voltage does not leak therefrom, as shown in greater detail in FIG. 2. In addition, annular sealing members 11 and 12 are interposed between the circumferential annular flange 10a of the cover 10 and the annular end surfaces of the housing cap 9 and the housing base 6, respectively, to waterproof the whole distributor.
In the conventional housing structure shown in FIGS. 1 and 2, the waterproofing of the engaging portion of the high voltage tower 8 is not enough, although the waterproofing thereof has crucial importance due to the high voltage supplied thereto. Namely, the water entering from the ventilating holes (not shown), which are formed in the housing base 6 for the purpose of exhausting NOX, etc., may reach the engaging portion of the high voltage tower 8.